Oxo-bridged binuclear iron(III) complexes with NN′-bis(2-methylpyridyl)ethylenediamine and 2,2′ : 6′,2″ : 6″,2‴-tetrapyridyl

Abstract

Two oxo-bridged complexes of iron(III), having different configurations depending on the different conjugative capacity of the quadridentate nitrogen ligands used, have been isolated and characterized. They are formulated as cis-[{Fe(bmen)}₂O(H₂O)₂][SO₄]₂·H₂O and trans-[{Fe(tetpy)}₂O][SO₄]₂·7H₂O, in which pairs of iron(III) ions (S= 5/2) interact antiferromagnetically [bmen =NN′-bis(2-methylpyridyl)ethylenediamine and tetpy = 2,2′:6′,2″:6″,2‴-tetrapyridyl]. Evidence is produced that the dimeric form of both complexes also predominates in an aqueous medium. As the pH is increased, the stability between the oxo-bridged units of the two complexes in solution differs; this is briefly discussed in the light of the different stereochemical features of the molecu les.